匹配所有长度为 n 的连续数字 [英] Match all consecutive numbers of length n

问题描述

在我的例子中 n=4.

Where n=4 in my example.

我对 Regex 很陌生，现在已经搜索了 20 分钟.有一些有用的网站可以简化事情，但我不知道如何继续.

I'm very new to Regex and have searched for 20 minutes now. There are some helpful websites out there that simplify things but I can't work out how to proceed with this.

我希望从中提取 4 个连续数字的每个组合:

I wish to extract every combination of 4 consecutive digits from this:

12345

获得:

1234 - possible with ^\d{4}/g  - Starts at the beginning
2345 - possible with  \d{4}$/g - Starts at the end

但我不能两者兼得！输入可以是任意长度.

But I can't get both! The input could be any length.

推荐答案

您的表达式没有按预期工作，因为这两个子字符串重叠.

Your expression isn't working as expected because those two sub-strings are overlapping.

除了零长度断言之外，输入字符串中的任何字符都将在匹配过程中被消耗，导致找不到重叠匹配.

Aside from zero-length assertions, any characters in the input string will be consumed in the matching process, which results in the overlapping matches not being found.

您可以通过使用前瞻和捕获组来检索重叠匹配来解决此问题.这是有效的，因为前瞻断言(以及后视断言)被归类为零长度断言，这意味着它们不消耗匹配；从而允许您找到任何重叠的匹配项.

You could work around this by using a lookahead and a capturing group to retrieve the overlapping matches. This works because lookahead assertions (as well as lookbehind assertions) are classified as zero-length assertions, which means that they don't consume the matches; thereby allowing you to find any overlapping matches.

(?=(\d{4}))

这里是一个简短的片段，演示了这一点:

Here is a quick snippet demonstrating this:

var regex = /(?=(\d{4}))/g;
var input = '12345678';
var match;

while ((match = regex.exec(input)) !== null) {
    if (match.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    console.log(match[1]);
}

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